The Australian government has continued to maintain there is no concrete evidence of a link between the chemicals and adverse health impacts, but has been criticised for the inadequacy of its response.

The government’s stated position sits in stark contrast with a view expressed this week by a senior official in the US Centres for Disease Control and Prevention (CDC), a government agency and the country’s leading public health institution.

Patrick Breysse, director of the CDC’s National Centre for Environmental Health, described the chemicals as “one of the most seminal public health challenge for the next decades”, according to the Bloomberg news agency.

'Children are being poisoned': fury at scandal of toxic firefighting chemicals

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Breysse estimated 10 million Americans were currently drinking contaminated water.

He said soon “we think that hundreds of millions of Americans will be drinking water with levels of these chemicals above levels of concern”, according to Bloomberg.

The comments have renewed calls for governments across the globe, including Australia, to urgently investigate the extent of drinking water contamination.

Rob Billott, the lawyer who led the US class action against Pfas user Dupont, has been pushing in recent months for the CDC to more thoroughly investigate the chemicals.

He said the comments from Breysse should be quickly acted upon.

“This reaffirms the importance of thoroughly – and promptly – investigating and addressing the threat that these chemicals present to human health when they are found in our drinking water supplies,” he told Guardian Australia.

The Australian government is currently facing two class actions from residents in contaminated communities: Oakey in Queensland and Williamtown in New South Wales.

Urgent action has been taken to provide bottled water and a treatment facility for residents in Katherine, in the Northern Territory, after the drinking supply was contaminated.

Last wee, the ABC revealed a 1987 report to defence had warned of the potential toxicity of firefighting foam.